From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 51CF6167DA4 for ; Mon, 12 Aug 2024 08:23:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723450993; cv=none; b=pwDgMLVQDvaouUoASnh00uDhgHdMJhRP63hs4aheAMwcUknDfFiHOp+CttZl+e0VqZaXfve/0u+mNpi9ERo0eiWYAsDaN2Onb+/83Tn5dw2jAtMXYOBx87UhboQQjCQdxwz8cuiqx8KGxDFOBnQuV5s4XT7hTqOqImlB5R9F9wM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723450993; c=relaxed/simple; bh=VaLmEUyHle652KJMQ8Jf9SEMCh3CTYv5wKAEqoXeRpw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SeGCdv1vbvSv0+IvY/NubOYe4+CuQCYaOszQ9NW5sVp56Uu2FO4UXB+apHf2Q5xax/dpKi0wdfAv81SQNVT1cxFIk5JgVgI3T3ztmiuVHLoBLm0H+I+gZy6ZQ7BuGdLuqxMlhikj1UZIXBJe+PPL6tHdEZCkxSpDz3xEm9axVc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=HyS0//BA; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HyS0//BA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723450989; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=6oFPUJOyQIYSk1zWN2Nlk4Wwe+GrCKc+I4GMFTzXlIs=; b=HyS0//BAmfsqUfoU+fsgeZyYnOFiSaU6V3n+Mp8YQvoyGtGBzKtdejM1dERjL0xBqIskuZ 1NKjTLpAjVM6PfMBx8BfFlIkjyEmLotTaBilB2lCPzpWKjxtu060jW0DlP5+BT7UfcVyyz QIancfl4Wu7t4MO0JDFr2SkfZbS3/7Q= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-255-K3Cg_wpON4iwGOGA0b7nfQ-1; Mon, 12 Aug 2024 04:23:06 -0400 X-MC-Unique: K3Cg_wpON4iwGOGA0b7nfQ-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4280a39ecebso23782045e9.0 for ; Mon, 12 Aug 2024 01:23:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723450985; x=1724055785; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=6oFPUJOyQIYSk1zWN2Nlk4Wwe+GrCKc+I4GMFTzXlIs=; b=jD5XCZGbCKIBAIbqDxzr55Kd6h1rqVf68vMsF6QYtWGosOtJixV+ZyrHUbyzG6PLu3 V0uUlhtOBogVW+06Ag6GdUuQMvsSUJMUFU4JrutZX0L4ErYdE2pySw3w6fo2a4HQdRQL XYGrmuYYGGIEB0RYhEyGsccXhwyH2t6/OptFNiOAIOi3xyo09eJUXRPD9O65Qq90rqOT iFQtt06fFDh7ygmkpnS4WN1WyglGEWQH7zSCN4cdCRyVDOpxC+n3I4KfBrCtbF6avVjY y7c5LQTNS5JniXAUGl66fYCZPHIq2CmbPr55tBK+lx3D0Bn8yy4BtT5gLzIxvPPA8u4N sHJw== X-Forwarded-Encrypted: i=1; AJvYcCW2ExJSxycLeZpD9hZdNz5p/Sb0GR5qFgxa8MrPx7K7gwcFXnFYHE8Ek9GZwVyXklhxrsU/+jX6T2zRCyw=@vger.kernel.org X-Gm-Message-State: AOJu0YwPxZqKfLNyl3oEqEEda+gwCHIeg/hmsHYYBOuTlCCI3e8Dibhs +AyzN93bVQ/tcwOpmjJyoIM1KNyE/DvsHJjaRsGeXCHRZhUoELRlZBFl+tpNFZBodPo4JNxo4Ax lie3MpitKwLF5DSR2U0V5i19Kq08JHG5V66DQMcxHe7mZBAyE4aWNWOjoVoHA+g== X-Received: by 2002:a05:600c:1d92:b0:426:5e32:4857 with SMTP id 5b1f17b1804b1-429c3a56054mr71811005e9.0.1723450985137; Mon, 12 Aug 2024 01:23:05 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHuTVV0SfDJ0uIl3ra4DiN60msO+1NiP4ttJhEcXgZ2iJHFQTTfVqHcOn1tOn5ur/e13m6MxA== X-Received: by 2002:a05:600c:1d92:b0:426:5e32:4857 with SMTP id 5b1f17b1804b1-429c3a56054mr71810775e9.0.1723450984612; Mon, 12 Aug 2024 01:23:04 -0700 (PDT) Received: from ?IPV6:2003:d8:2f09:3f00:d228:bd67:7baa:d604? (p200300d82f093f00d228bd677baad604.dip0.t-ipconnect.de. [2003:d8:2f09:3f00:d228:bd67:7baa:d604]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4290c77510asm185261545e9.33.2024.08.12.01.23.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Aug 2024 01:23:04 -0700 (PDT) Message-ID: <206a16e3-3dfb-40f2-9785-389bc330e44d@redhat.com> Date: Mon, 12 Aug 2024 10:23:02 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [linus:master] [mm] c0bff412e6: stress-ng.clone.ops_per_sec -2.9% regression To: Mateusz Guzik Cc: Yin Fengwei , kernel test robot , Peter Xu , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Andrew Morton , Huacai Chen , Jason Gunthorpe , Matthew Wilcox , Nathan Chancellor , Ryan Roberts , WANG Xuerui , linux-mm@kvack.org, ying.huang@intel.com, feng.tang@intel.com References: <202407301049.5051dc19-oliver.sang@intel.com> <193e302c-4401-4756-a552-9f1e07ecedcf@redhat.com> <439265d8-e71e-41db-8a46-55366fdd334e@intel.com> <90477952-fde2-41d7-8ff4-2102c45e341d@redhat.com> <6uxnuf2gysgabyai2r77xrqegb7t7cc2dlzjz6upwsgwrnfk3x@cjj6on3wqm4x> <5a67c103-1d9d-440d-8bed-bbfa7d3ecf71@redhat.com> <5c0979a2-9a56-4284-82d2-42da62bda4a5@redhat.com> <66c4fcc5-47f6-438c-a73a-3af6e19c3200@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 12.08.24 10:18, Mateusz Guzik wrote: > On Mon, Aug 12, 2024 at 10:12 AM David Hildenbrand wrote: >> >> On 12.08.24 06:49, Mateusz Guzik wrote: >>> On Mon, Aug 12, 2024 at 12:43:08PM +0800, Yin Fengwei wrote: >>>> Hi David, >>>> >>>> On 8/1/24 09:44, David Hildenbrand wrote: >>>>> On 01.08.24 15:37, Mateusz Guzik wrote: >>>>>> On Thu, Aug 1, 2024 at 3:34 PM David Hildenbrand >>>>>> wrote: >>>>>>> >>>>>>> On 01.08.24 15:30, Mateusz Guzik wrote: >>>>>>>> On Thu, Aug 01, 2024 at 08:49:27AM +0200, David Hildenbrand wrote: >>>>>>>>> Yes indeed. fork() can be extremely sensitive to each >>>>>>>>> added instruction. >>>>>>>>> >>>>>>>>> I even pointed out to Peter why I didn't add the >>>>>>>>> PageHuge check in there >>>>>>>>> originally [1]. >>>>>>>>> >>>>>>>>> "Well, and I didn't want to have runtime-hugetlb checks in >>>>>>>>> PageAnonExclusive code called on certainly-not-hugetlb code paths." >>>>>>>>> >>>>>>>>> >>>>>>>>> We now have to do a page_folio(page) and then test for hugetlb. >>>>>>>>> >>>>>>>>> return folio_test_hugetlb(page_folio(page)); >>>>>>>>> >>>>>>>>> Nowadays, folio_test_hugetlb() will be faster than at >>>>>>>>> c0bff412e6 times, so >>>>>>>>> maybe at least part of the overhead is gone. >>>>>>>>> >>>>>>>> >>>>>>>> I'll note page_folio expands to a call to _compound_head. >>>>>>>> >>>>>>>> While _compound_head is declared as an inline, it ends up being big >>>>>>>> enough that the compiler decides to emit a real function instead and >>>>>>>> real func calls are not particularly cheap. >>>>>>>> >>>>>>>> I had a brief look with a profiler myself and for single-threaded usage >>>>>>>> the func is quite high up there, while it manages to get out with the >>>>>>>> first branch -- that is to say there is definitely performance lost for >>>>>>>> having a func call instead of an inlined branch. >>>>>>>> >>>>>>>> The routine is deinlined because of a call to page_fixed_fake_head, >>>>>>>> which itself is annotated with always_inline. >>>>>>>> >>>>>>>> This is of course patchable with minor shoveling. >>>>>>>> >>>>>>>> I did not go for it because stress-ng results were too unstable for me >>>>>>>> to confidently state win/loss. >>>>>>>> >>>>>>>> But should you want to whack the regression, this is what I would look >>>>>>>> into. >>>>>>>> >>>>>>> >>>>>>> This might improve it, at least for small folios I guess: >>>> Do you want us to test this change? Or you have further optimization >>>> ongoing? Thanks. >>> >>> I verified the thing below boots, I have no idea about performance. If >>> it helps it can be massaged later from style perspective. >> >> As quite a lot of setups already run with the vmemmap optimization enabled, I >> wonder how effective this would be (might need more fine tuning, did not look >> at the generated code): >> >> >> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h >> index 085dd8dcbea2..7ddcdbd712ec 100644 >> --- a/include/linux/page-flags.h >> +++ b/include/linux/page-flags.h >> @@ -233,7 +233,7 @@ static __always_inline int page_is_fake_head(const struct page *page) >> return page_fixed_fake_head(page) != page; >> } >> >> -static inline unsigned long _compound_head(const struct page *page) >> +static __always_inline unsigned long _compound_head(const struct page *page) >> { >> unsigned long head = READ_ONCE(page->compound_head); >> >> > > Well one may need to justify it with bloat-o-meter which is why I did > not just straight up inline the entire thing. > > But if you are down to fight opposition of the sort I agree this is > the patch to benchmark. :) I spotted that we already to that for PageHead()/PageTail()/page_is_fake_head(). So we effectively force-inline it everywhere except into _compound_head() I think. But yeah, measuring the bloat would be a necessary exercise. -- Cheers, David / dhildenb